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Accumulated Other Comprehensive Income (Reclassifications Out of Accumulated Other Comprehensive Income (Loss)) (Details) - CAD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Non-regulated fuel for generation and purchased power | $ 225 | $ 209
Income (Loss) from Equity Method Investments | 154 | 124
Operating, maintenance and general | 1,564 | 1,372
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest | 816 | 819
Income tax expense (recovery) | 69 | 520
Net income | 747 | 299
Reclassification out of Accumulated Other Comprehensive Income [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Net income | (1) | 47
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest | (6) | 7
Income tax expense (recovery) | 0 | 1
Net income | (6) | 8
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] | Power and Gas Swaps [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Non-regulated fuel for generation and purchased power | (1) | (3)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] | Foreign Exchange Forward [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Regulated | (5) | 10
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest | 7 | 36
Income tax expense (recovery) | 2 | 4
Net income | 9 | 40
Reclassification out of Accumulated Other Comprehensive Income [Member] | Defined Benefit Plans Adjustment, Net Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Operating, maintenance and general | 25 | 33
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Including Portion Attributable to Noncontrolling Interest [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Operating, maintenance and general | (1) | (8)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Transition Including Portion Attributable to Noncontrolling Interest [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Pension and Other Postretirement Benefit Expense | (17) | 11
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Available For Sale Securities Gain Loss Including Portion Attributable To Noncontrolling Interest [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Other Income (Expense) | 0 | (1)
Net income | $ (4) | $ (1)

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